This question has been asked many times here.
There are a few points you need to keep in mind.
1) There is not automatic, easy (one-button) tool to copy your Kunena
forum from one site to another. Even though no tool exists that will copy a forum from one site to another, if you are familiar with how Joomla and Kunena
work together, it is not too difficult to move a forum from one site to another site.
2) Kunena consists of three parts:
- the user database tables
- the database tables that hold the sections, categories, topics, messages, polls, subscriptions, etc.; and
3) Moving a forum from J! 1.5 to J! 3.x
requires changing the user database changes. This must be done before you can move the Kunena database tables.
4) Because J! 1.5 does not know anything about ACLs, after you have moved your forum to your new J! 3.x site you need to apply ACLs to all your Kunena
sections and categories otherwise you and your users will not be able to post messages.
If this sounds like hard work it's not. It's not hard work. It is time-consuming work. On average, it takes about 3-5 hours to migrate a forum from J! 1.5 to J! 3.x
and, depending on large your forum is, it can take a few hours after that to test that everything works.
If you are prepared to do this work yourself then you can probably do the job in a day. If you would rather someone else did this job for you, there are plenty of people who can perform this service for you for a reasonable price.
For further information about this topic, please see
How to move, copy or merge my old Kunena forums from one site to another
If you have any questions, please use that topic to ask them.